ITW Trans Tech: How To Design With Pad Printing In Mind

PADPRINT NOTEBOOK
USEFUL TIPS & INFORMATION
© ITW Trans Tech
An Illinois Tool Works Company



	Design Tip: Ask The Experts In the past 20 years, ITW Trans Tech has test- printed and built pad printing systems for thousands of customers. Our print lab and engineering staff have solved printing problems from A to Z over a wide range of products and industries. Chances are that someone else has already tried something similar to what you are doing. Why re-invent the wheel? Just ask us. Our experts can bring their wealth of experience to even the toughest application. We might even give you a few tips before you start designing. Any questions? Call us today at 630.752.4000 or e-mail us! Time To Re-Tool? Ask Our Experts! For Tooling, Re-Tooling or Fixture information: Retooling Supervisor: Owen Ault 630.909.5777

Frequently Asked Questions:
How To Design With Pad Printing In Mind

IN the manufacturing process,
there are countless factors that need to be considered when designing your parts: Who will make the mold? Of what material will the product be made? Which internal components will be used? How should it be assembled? What color should it be? How should it be packaged? And so on... One of the last operations to be done is decorating. So how do you design with pad printing in mind?

sample products before pad printing

Some typical three-dimensional parts prior to decorating.

At the start of the process, it is important that designers of the product have given the pad printing process the necessary considerations in their plans. Here are several things that need to be kept in mind about part design to get a good printed part:

The "Ideal" Design
When the silicone transfer pad compresses on a flat cliche plate and picks up the image, the best way to avoid distortion is to print on a flat surface. Of course, the ideal print job would consist of a completely flat, white ABS part with a slightly matte finish, receiving a two-inch diameter image using single component black ink and no heat cure. And of course, this is rarely the case.

radius diagram

The radius range of the pad-printable area of a spherical part.

Shapes: Radius & Contour
These days, most three-dimensional parts have all sorts of contours and radiuses (or is it radii?) that can make pad printing quite a challenge. A simple rule to follow for printing on a true radius (like a golf ball or a cylinder) is to use a maximum 90-degree wrap. However, you may even be able to go as far as 120 degrees, depending on the image shape.

contour diagram

The contour limits of a part profile; B= the depth of a recess; A= the set-back from a vertical wall.

Also, keep in mind that there may be some stretch of the image as the pad compresses around the radius. If so, the artwork may require some deliberate distortion and further test printing to achieve an acceptable print.

Texture
The majority of parts that we decorate have some kind of surface texture. It can be a molded-in texture or a spray-painted texture. The style and depth of the texture can have a great affect on the print outcome. We may not be aware of it, but on a microscopic level, texture is actually a series of peaks and valleys. When we try to print a layer of ink (approx. .0005” thick) on top of peaks and valleys, the result is a canopy effect that bridges across from peak to peak. We may have to use a steeper pad with a harder durometer to get down into the “valleys” and lay down sufficient ink.

texture diagram

The texture limits of a part showing the depth of the surface cavities.

Many times that doesn’t happen and there is an air pocket under the canopy. Two things can happen to cause an unacceptable print: either the ink canopy tears and causes a pinhole, or the air pocket under the canopy heats up and tears due to heat curing of the part after printing. We recommend that the texture be .001” to .002” maximum for optimum printing results. Double or triple hits (layers of ink) may also improve print appearance and eliminate pinholes.

Recesses
Occasionally, a product will have a vertical sidewall and the image location is very close to the wall. This situation makes it difficult to fit a standard transfer pad close enough to the wall to print the image. This is because the pad, when compressed, bulges on the sides and hits the sidewall of the part. This can cause print distortion, which, in order to compensate for, may require an artwork distortion with a test printing study.

recess diagram

The recess limits of a part: M=depth of recess; A=distance from vertical wall; with vertical wall angle greater than 90 degrees.

We can try to avoid distortion in this case by designing a custom transfer pad in which the sides have a back draft. When such a pad is fully compressed, the sides will not touch the vertical wall of the part. A general rule of thumb to follow is that the artwork must be at least as far away from the wall as the height of the wall. However, each application must be evaluated individually.

Raised Letters
Some molded parts have raised letters that need to be printed on. Generally we recommend that the mold be redesigned with the raised letter removed and the image printed directly on a flat surface. However, when raised letters are required, there are key items to consider. It’s important to know how close to the edge of the letters the image will go. This is critical, due to the difficulty of exact print repeatability. With multiple mold cavities, the related molding tolerances may vary slightly.

raised lettering diagram

Diagram of pad function and proper support required for pad printing on raised letters.

As a result, the exact location of the raised letters, when the part is loaded onto the holding fixture, may also change. Even a tiny variation can cause the location of the printed image to be off which can leave unprinted ink remaining on the pad. This excess ink, left unprinted on the first part, can build up and later be printed on another part with undesirable results. In the worst case scenario, separate artwork for each cavity of the mold would be needed but is not very practical. So, if you can design a reasonable gap between the edge of the part and the edge of the art, you can leave enough tolerance for a repeatable process.

Material Choice
When a product is designed, the choice of material or substrate relates to the function of that part and how it will be used. There probably is not a lot of thought given to whether it can be easily pad printed. Trans Tech carries approximately 30 different types of ink to accommodate the myriad of substrate materials used today. We are also constantly testing new inks to answer the changing needs of industrial decorators.

Some of the more common materials that are difficult to print on are: acetal, polyester, nylon, phenolic, polypropylene, and polyethylene. These types of materials will probably need either surface pretreatment, heat curing, or both in order to enable the ink to adhere to the substrate.

On the other hand, some easier materials to padprint are: ABS, PVC and polystyrene. We always recommend that you submit samples for testing to our print lab if you are having trouble with ink-to-substrate compatibility.

pad printed samples

A wide array of applications are possible when properly designed with pad printing in mind.

Ask The Experts
In the past 20 years, Trans Tech has test- printed and built pad printing systems for thousands of customers. Our print lab and engineering staff have solved printing problems from A to Z over a wide range of products and industries. Chances are that someone else has already tried something similar to what you are doing. Why re-invent the wheel? Just ask us. Our experts can bring their wealth of experience to even the toughest application. We might even give you a few tips before you start designing. Call us today!

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